Sept/Oct 2009

Innovations in tailings management

The oil sands industry is moving towards reducing water use and advancing reclamation time

By
M. Eisner

EarthRenew CEO Christianne Corin and president and COO Al Fedkenheuer holding bucket of fertilizer at the Strathmore facility

Last February, Alberta’s Energy Resources Conservation Board (ERCB) issued a new directive outlining aggressive criteria for managing tailings in the oil sands industry. Among other things, the ERCB focused attention on reducing fluid fine tailings at oil sands operations and set timelines for reclamation of designated disposal areas. These measures are aimed at accelerating the transformation of tailings into reclaimed land.

There are currently more than 130 square kilometres of tailings disposal areas in the oil sands region. After open pit mining, hot water is used to separate very heavy oil (bitumen) from the sticky sand. Following its use in the process, this water — which also contains clay, sand and residual bitumen — is then sent to a tailings pond, often a discontinued mine pit. A percentage of the tailings water is recycled back for use in the bitumen extraction process.

Several research facilities and businesses have been developing and applying new reclamation techniques and attempting to reduce the use of fresh water in oil sands extraction.

Water, water everywhere

Shell Canada’s Athabasca Oil Sands project in northern Alberta exemplifies the company’s efforts to produce “trafficable” tailings. Such tailings can eventually be walked on or driven over, and can go a long way in meeting the objective of accelerated reclamation of excavation pits and tailings ponds.

In 2008, Shell commissioned a $100 million tailings pilot plant at the Muskeg River mine in order to meet the new government guidelines. “While the directive is technically challenging, Shell has invested substantially in tailings research,” says Laurieanne Lynne, communications advisor, Corporate Shell Canada Limited. “Engineering work started before the ERCB issued its tailings directive as part of Shell’s commitment to sustainable oil sands development. So far, the results of our efforts to create trafficable tailings have been encouraging.”

One of the goals is to improve fresh water management at Shell’s oil sands mining operations and the Scotford Upgrader. New technologies and processes are being developed to increase water treatment, recycling and storage at both facilities. Shell typically uses large volumes of water, primarily from the Athabasca River, to separate bitumen molecules trapped in the sand and clay. “On average, the oil sands industry uses two to three barrels of fresh water to extract one barrel of bitumen,” Lynne reports. “But we work hard to manage our water use by recycling as much water as possible from the tailings ponds.”

All water recovered from the tailings ponds and within the process is recycled back through the operation. Nevertheless, some of it is lost to evaporation and to the interstices between clay and sand particles that were originally occupied by the bitumen. For even more significant reduction in the use of fresh water, the water loss has to be minimized. This is another reason why Shell is developing technologies to produce drier tailings. Currently, Shell’s tailings ponds measure about 12 square kilometres, with a government-approved extension underway.

And while the tailings get drier and drier, Shell is also recycling water more diligently. At the Scotford Upgrader, effluent from a wastewater treatment plant is being reused, resulting in a 10 to 15 per cent reduction in its water intensity. The company is also exploring opportunities to implement a “zero liquid discharge” system.